Lethargic, wont eat or drink, throwing up, and has diarreah

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Houndy is my foster dog who is about 10 years old and weighs around 80 pounds.

Houndy was doing well and showing no signs of illness until Saturday and Sunday. The only thing I noticed prior to Saturday is throughout last week, Houndy would skip a meal. He would either skip breakfest and eat dinner or eat breakfest and skip dinner. He loves food, so I thought that was weird. Saturday, we were heading to an adoption event, he wouldn't eat. I wanted him to eat something so he wouldn't be starving. I gave him a small bowl of proplan dog food (his normal food Blue Buffalo Weight Control). He chowed that down and we went to the adoption event. Then at the adoption event he got a rawhide bone - not my idea. I cannot stand rawhide. Anyway, he chowed that down and it was gone in 20 minutes. I'm really worried about an intestinal blockage or maybe he just has a sensitive stomach and giving him a different food so sudden caused him an upset tummy? We keep the garbage up high, so he couldn't have got anything from there. Those are the only 2 things I can think of - the bone and the food.

Houndy had diarreah outside at 8 am Sunday morning. The throwing up didn't start until Sunday afternoon around 4. He threw up once in my mom and dad's room. Then around 7 pm, there was 3 HUGE piles of throw up in the dining room. Houndy went to my room to sleep and didn't even move until 2:30 in the morning when he went in the dining room and threw up 2 piles of throw up and 1 pile of diarreah.

He has me worried. We are probably going to take him to the vet tomorrow, but I thought I would come here for advice first. Thanks!!

Houndy is doing a LOT better now. He has not thrown up for almost 24 hours. I think it was just the different brand of dog food that upset his stomach and that was just a one time thing (I didn't want him to be hungry at the adoption event).